Recently, together with a rapid advance of computer and internet technology, a large number of digital works are produced and distributed. In this regard, copies or modified ones of such digital works identical to the original works can be easily made without authorization from the author. Accordingly, techniques for preventing illegal copying of the digital works and the distribution thereof are being attempted in various manners.
A watermarking technique, one of the above techniques, is a technique which inserts information identifiable only by author into the various digital works such as image, audio, video, etc. so as to extract the author information hidden in the digital works for determining the authenticity of such digital works when such digital works are used or distributed without permission of the author. In case of confirming the original owner such as in ownership conflict, etc. in the stage of circulation of digital works, i.e. digital contents, such technique allows the extraction of watermark inserted in the digital contents so as to arrange basis for enforcing rights such as the ownership, copyright, etc.
The conventional watermarking technique provides an advantage of protecting the copyright information while concealing and inserting the information with regard to the contents in order for users to be unaware of such inserted information. However, such technique has a drawback of the amount of information which can be inserted is not as much as desired.
Further, barcode commonly used in every field of industries nowadays was originally invented for the purpose of increasing the management efficiency of the supermarkets, reducing the time spent waiting at the counter, and automatically making a new record of inventories concurrently with the sales. As the barcode showed a big success in its application in the field of retails, other fields of industries began to adopt barcode gradually.
Barcode is classified into continuous type and discrete type in terms of the method of expressing the symbols thereof. The discrete type barcode has each of its characters independently separated, has gap between these characters, and refers to a barcode symbology in which each character starts with a bar and ends with the bar. When such type of barcode is decrypted, the decrypting process is carried out by each character. The continuous type barcode, unlike the discrete type symbology, does not have gap between each character, and refers to a barcode symbology in which each character starts with a bar and ends with space. The end of the character of the continuous type barcode is distinguished by the beginning character of the next character.
Also, barcode is classified into one-dimensional (linear) barcode and two-dimensional barcode in terms of the method of arranging the data. The two-dimensional barcode may be further classified into multiple layer type, matrix type, circular type, hexagonal type, color barcode type, etc. in terms of the shape and arrangement of the bar.
Such conventional barcode is a widely used in every field of industries, which provides an advantage of inserting symbols by using simple symbol structure so as to increase management efficiency, and to easily obtain information with respect to the products. However, such barcode has a drawback as it is difficult to verify whether the barcode has been forged or altered because the barcode is exposed visually and it uses a method of either being attached to the products or printed on the products.
Moreover, as the scope of using barcode is gradually expanding, barcode is used for classifying important document used in the government and public offices or products requiring safety or security such as nuclear wastes as well as the conventional products. Therefore, forgery or alteration of the barcode may bring serious problems according to the expansion of scope of use of barcode. This is because only a simple replacement with other barcode can result in a forgery of the content of the barcode.